The present invention provides compounds and a method by which the yield of certain plants, particularly crop plants, can be improved by applying to such plants a yield-improving amount of D- or DL-.alpha.-O,O-diethylphosphorodithioylacetylphenylglycine ethyl esters, described herein. The plants for which the present invention has been found especialy useful are the legumes, e.g., soybeans, peas, peanuts and clover.
The application of the D or DL-.alpha.-O,O-diethylphosphorodithioylacetylphenylglycine ethyl esters improve the yield of legumes as much as about 15 percent. The term "yield" means dry weight of harvested pods of the legume crop plants. The yield per plant and the yield per acre is improved by application of the compound of this invention.
The term "soybean" includes both the determinate type (e.g. Bragg) which is grown in the southern United States, and the indeterminate type (e.g. Corsoy or Williams) which is grown in the northern United States and Canada. Generally, the determinate varieties of soybeans grow very little after flowering, if at all, and branch more profusely than indeterminate varieties. Indeterminate varieties increase their height by two to four times after flowering begins.